The present invention relates to a method and apparatus for testing a catalyst material. While the invention may be used for the ageing of a catalyst converter, it may have other applications as well.
Catalyst material is used in many locations and processes. One common example is catalyst material used in a catalytic converter for the exhaust stream of an internal combustion engine in vehicles, such as cars, motorcycles, trucks, etc. Other catalyst material processes and applications include those in the chemical and petrochemical industries, electricity generators, utility engines, marine applications, aerospace applications, etc.
Catalytic converters are most commonly known for use in automobile exhausts to reduce the toxicity of emissions from an internal combustion engine. Its purpose is to reduce levels of harmful gases, such as carbon monoxide (CO), hydrocarbons (HC) and various oxides of nitrogen (NOx), by converting them into carbon dioxide (CO2), water, nitrogen and oxygen.
A common catalyst material used in a catalytic converter consists of a fine layer of precious metal(s) dispersed on a carrier layer of highly porous alumina, (Al2O3), washcoat, which in turn is bonded to a ceramic substrate. Other carriers that are commonly used as an alternative to alumina are silicon dioxide, (SiO2), Titanium Dioxide, (TiO2) and Zeolites (aluminium, silicon and oxygen compounds); however alumina remains the most popular choice. The substrate can come in a pellet or monolithic form: however the honeycomb monolithic structure is the most widely used. The material used in this type of structure can also vary. Some catalyst manufacturers opt for metallic monoliths which are composed of temperature-resistant aluminium-coated steels, while most choose the ceramic structure. The most common precious metals for such catalyst material in this application are Platinum, Pt, Palladium, Pd, Rhodium, Rh and Vanadium Oxide, V2O5.
Due to increased public awareness in the environmental issues, governments are constantly updating emissions legislation by introducing more stringent emissions regulations for automobiles. Thus, there is increasing attention to and testing of catalytic converter performance, such as their ageing and lifetime.
One method of testing a catalytic converter is to continuously run an internal combustion engine in a test facility and to locate the catalyst in its exhaust. Public examples include the ZDAKW Ageing Cycle (European Commission Joint Research Centre), the LNT Ageing Cycle (Oak Ridge National Laboratory), and the STRAW-MAN Ageing Cycle, although manufacturers also develop their own cycles and normally these are not in the public domain and are considered ‘trade secrets’.
However, the operating costs of fuel to fully age a catalytic converter to the point of deactivation can be $50,000 or more.
US2005/0204804 A1 discloses a method for artificially ageing a catalyst device for use on a catalyst test bench for converting exhaust gases. Hot ageing gas is provided by a burner, such as a gas turbine, and gas which emerges from the catalyst device is partially recirculated and admixed with the ageing gas to be fed to the catalyst device.
One problem with the invention shown in US2005/0204804 A1 is that the majority of the hot ageing gas is still based on combustion of a C-containing fuel, i.e. petrol, diesel or another gasoline material, which is then combusted in a burner. Significant costs are still required to provide such a fuel.
A second problem with the invention shown in US2005/0204804 A1 is that the combustion of a C-containing fuel requires a burner, which must be controlled within the test bench environment. Combustion of a fuel on a test bench scale does not provide accurate control of the proportions of gas constituents going to the catalyst device.